Head assembly for liquid fuel catalytic beater

ABSTRACT

A liquid fuel catalytic heater has a head assembly including a catalytic element having outer wall portions which are straight and generally upright in the direction of combustion air flow over 50 to 75 percent of the combustion area to effect more efficient heating and to radiate heat laterally of the catalytic element through a guard canopy.

United States Patent Hefling et al. Apr. 8, 1975 [54] HEAD ASSEMBLY FORLIQUID FUEL 3,240,256 3/l966 Binkley el al 431/328 CATALYTIC BEATER3,343,586 9/1967 Berchtold et a] 431/350 3,457,02I 7/1969 Gladden et al..r 431/350 [75] Inventors: Dennis Very! g; Richard 3,734,682 5/1973 May431 329 Douglas Curtis; Floyd 0. Cruver, Jr., all of Wichita, Kans;David J. FOREIGN PATENTS R APPLICATIONS Gladden, Dearbom- Mlchl,095,865I2/l954 France 431/328 [73] Assignee: The Coleman Company, Inc.,

wlch'mi Kans- Primary Examiner-Carroll B. Dority, Jr. 22 Filed; No 51973 mmiey, Agent, or FirmDawson, Tilton, Fallon &

un mus [2l] Appl. No.: 412,585 g Related U.S. Application Data [63]Continuation of Ser. No. 221,327. Jan. 27. 1972, [57} ABSTRACT uhurdonedA liquid fuel catalytic heater has a head assembly including a catalyticelement having outer wall portions 431/329 25 5 4 3 which are straightand generally upright in the direc- 5 i B 431/350 tion of combustion airflow over to percent of 0 can 43'l/326 328 the combustion area to effectmore efficient heating and to radiate heat laterally of the catalyticelement [56] References Cited through a guard canopy UNITED STATESPATENTS 6 Claims, 2 Drawing Figures 3,217.70l ll/l965 Weiss 43l/329 HEADASSEMBLY FOR LIQUID FUEL CATALYTIC HEATER RELATED APPLICATION This is acontinuation application of copending application Ser. No. 221,327,filed Jan. 27, 1972 and now abandoned.

BACKGROUND AND SUMMARY This invention relates to catalytic heaters; andmore particularly, it relates to an improved head assembly for aportable catalytic heater which operates on a refillable liquid fuelcharge.

Portable liquid fuel catalytic heaters have been known in the art forsome time. Typically, a porous catalytic element having a catalystimpregnated on its outer surface partially defines a fuel vapor chamberwherein fuel is vaporized. The fuel is fed to the chamber by a wickwhich conducts liquid fuel from a tank located beneath the headassembly. Such portable liquid fuel catalytic heaters characteristicallyhave a catalytic element in the form of a hemisphere or dome which issurrounded by a guard canopy having a cylindrical side skirt of metalwhich directs room air for combustion onto the catalytic element. Theprimary heat transfer mechanism in this type of catalytic heater isthrough convention currents. One such heater is disclosed in theBerchtold, et al., re-issue US. Pat. No. 26,976.

In the present invention. a portable liquid fuel catalytic heater has ahead assembly wherein the catalytic element is formed, preferably bymolding, into a shape having a generally upright side wall offrusto-conical shape and a slightly domed top. Preferably, theinclination of the side wall forms an angle in the range of 3-l5 withthe vertical, and the height of the slightly domed top is less thanabout one-fourth the height of the side wall portion. A canopy isprovided in the heater which covers the head assembly and it includes agenerally cylindrical skirt portion; however, the skirt portion of thecanopy contains large windows laterally of the side wall of thecatalytic element.

It has been found with the improved head construction of the presentinvention, that most of the combustion takes place at the side wall ofthe catalytic element and that a relatively minor portion of combustionoccurs at the top. Because of the straight shape of the side wallparallel to its axis, combustion air traveling upwardly along the sidewall tends to have a reduced velocity, and this has been found tosignificantly enhance the efficiency of combustion of the vapor passingthrough the side wall of the porous catalytic element. Further, lateralheating by radiation is greatly enhanced with the present constructionbecause most of the combustion takes place at the side wall and there isa relatively unimpeded radiation path laterally of the side wall. Thisis of particular advantage in a tent, for example, wherein personsgathered around the heater can be warmed through radiation. As hasalready been mentioned, lateral radiation heating with previouscatalytic heaters has been minimal.

It is also preferable to have a slight dome shape at the center of thetop portion of the catalytic element in order to facilitate lighting ofthe heater in a wind.

Normally, portable liquid fuel catalytic heaters having a domedcatalytic element exhibit an area at the very top where combustion isreduced. This is caused by the upward flow of combustion air at thispoint, away from the surface of the catalytic elements. This issometimes referred to as the dead area." It has been found that with theshape of the catalytic element of the present invention, the dead areaat the top center of the catalytic element is greatly reduced.

Other features and advantages of the present invention will be apparentto persons skilled in the art from the following detailed description ofa preferred embodiment accompanied by the attached drawing.

THE DRAWING FIG. 1 is an upper perspective view of a liquid fuelcatalytic heater constructed according to the present invention with aportion of the head assembly and its support tube cut away; and

FIG. 2 is a vertical cross sectional view of the catalytic element ofthe heater of FIG. 1.

DETAILED DESCRIPTION Referring then to the drawing, FIG. 1 shows aportable liquid fuel catalytic heater including an upper head assemblygenerally designated by reference numeral supported on a tube 11 which,in turn, is secured by means of a bayonet lock generally designated 12to a collar 13 mounted to the top ofa fuel tank or reservoir 14 whereinliquid fuel is stored. The fuel tank 14 is, of course, refillable.

A canopy generally designated by reference numeral 15 encompasses thehead assembly 10, and a snuffer (not shown) is also provided forcovering a catalytic element 16 in the head assembly 10 when it isdesired to stop combustion.

The catalytic element I6 includes a frusto-conical side wall 17 and adomed top 18 integral with the side wall 17. An outwardly extending footflange I9 is formed at the bottom of the side wall 17.

The catalytic element 16 is preferably formed from non-combustiblefibers such as ceramic fibers which are vacuum formed into the shapethat has been illustrated. A slurry ofthe fibers together with a bindersuch as a starch adhesive or colloidal silicone is drawn into a die ofthe desired shape by means of a vacuum. This forms a porous, felt-likebase through which fuel vapor is transmitted. The surface of the base isthen impregnated with a catalyst, such as platinum, according toconventional means. The present invention is not limited, however, toany particular base material nor to a specific catalyst; but, rather,this invention relates to improvements in the shape of the catalyticelement and the advantages resulting therefrom.

The catalytic element 16 may also be provided with an exterior wire meshscreen designated 20 in FIG. 1. The catalytic element 16 partiallydefines a fuel vapor chamber generally designated 21 at the center ofwhich there is a wick 22. The wick 22 is surrounded at its intermediatesection with a vertically slidable tube 23 to which there is attached awick-adjustment mechanism generally designated by reference numeral 24and including a yoke 25 which is adjustable upwardly and downwardly froma position outside of the support tube 11 to move the adjustment tube 23to cover more or less of the portion of the wick 22 within the fuelvapor chamber 21. The bottom portion of the wick 22 extends downwardlyinto the reservoir 14 and conducts liquid fuel upwardly into the fuelvapor chamber 21. The fuel then vaporizes from the exposed portion ofthe wick 22 and passes through the catalytic element 16, combustionoccurring at the outer surface thereof.

A head bottom 27 is attached to the top of and supported by the supporttube 11. The bottom 27 includes a peripheral recess 28 for receiving theoutwardly extending foot portion 19 of the catalytic element 16. As bestseen in FIG. 1. the catalytic element and the screen 20 are held inplace by crimping the outer portion of the head bottom 27 over the topof the foot flange 19.

Resting on top of the head bottom 27 and secured to it as with spotwelding is a head support 29 which extends inwardly to form a centralaperture 30 through which the adjustment tube 23 is raised and lowered.The head support 29 forms a pan which is filled with Fiberglasinsulation material 31 which, in turn, is covered with a sheet of tinfoil 32. The tin foil 32 and insulation material 31 are held in place bymeans of tabs 34 which are formed in the head bottom and extend upwardlythrough the insulation material and tin foil and then crimped over tohold them in place.

The canopy is secured to the top of the reservoir 14 in a suitablemanner permitting it to be pivotally moved to uncover the catalyticelement 18 for starting. The canopy 15 includes a plurality of upwardlyextend ing windows 38 which extend upwardly from a lower skirt 39 toprovide at least 50 percent free space later ally of the side wall 17 ofthe catalytic element 16. Since most of the combustion takes place atthe side wall 17 in this construction, as will be explained more fullybelow, the placement of the windows 38 and the large openings providedthereby greatly facilitate the radiation of heat from the surface oftheside wall 17 so that persons gathered around the heater may be warmed byradiation. The top of the canopy 15 includes a screen 40 through whichheated room air and combustion products move.

Turning now to HQ. 2, the frusto-conical shape of the side wall 17 ofthe catalytic element 16 can be better appreciated. An angle, indicatedas .r, is formed between the outer surface of the side wall 17 and averti- :al line. This inclination is primarily to facilitate removal ofthe vacuum-formed catalytic element from its mold; the primary functionof the upright shape of the side wall is to promote lateral heatingthrough radia- Zion. Thus, the angle .r may be varied within the range 15, although for the reason mentioned, it is prefera- Jly greater thanabout 3.

Combustion air is drawn in beneath the lower skirt 39 )fthe canopy 15,in the direction ofthe arrows 43, and :ombustion takes place primarilyat the outer surface )f the upright side wall 17. Because the combustioniurface is straight in the direction of flow of combus- :ion air and itis generally parallel to the flow lines. the noting combustion air tendsto cling to the outer surace and reduce its velocity. This promotes amore :omplete combustion. and significantly contributes to he improvedburning efficiency of the heater. Tests no on heaters constructedaccording to the present inention demonstrate that fuel vaporizing fromthe wick l2 flows primarily outwardly in a radial direction, herebyindicating that most of the combustion takes ilace at the side wall 17of the catalytic element. Furher, after the heater has heatedsufficiently, the outer urface of the side wall 17 glows with a muchbrighter ight than does the top 16. Thus, heating by lateral radittion,as diagrammatically illustrated by the sinusoidal arrows 44 issignificant and can be felt by persons located beside the heater.

It has been found that significant radiant heating to the side of theheater is best achieved if the total surface area of the side wall 17 isin the range 50-75 percent of the total exposed area of the catalyticelement 16, and preferably within the range to percent. Another designparameter that has been found important is the ratio of the height ofthe side wall 17 (as indicated by the arrow 1 in FIG. 2) to the heightof the slightly domed top 18. The dead area at the center of the top 18surprisingly has been found to be minimized when the ratio z/y ismaximized; however, if the top 18 were perfectly flat even though thedead area would be at a minimum, a difficulty arises in lighting theheater, Normally, lighting is accomplished by swinging the canopy 15 touncover the catalytic element 16 and placing a small amount of fuel onthe center portion of the top 18 and lighting it, It has been found thatif the top 18 is perfectly flat, lighting of the heater in the windbecomes difficult because the wind tends to blow the flame out. However,by a slight doming of the type shown in FIG. 2, lighting is facilitatedwhile keeping the dead area to a minimum, Preferably, the ratio of theheight of the side wall to the height of the top 2/ is less than about4/].

Another advantage of the present invention is that the time betweenstarting and attaining normal operating temperature for the catalyticelement is reduced, and this is due at least in part to the reduced massof the element. The need for an interior wire screen, as prior elementsrequired, has been eliminated because the inventive element is moldedinto its shape and retains it without such screen,

Thus, with the present invention, a portable liquid fuel catalyticheater has been found to exhibit a more efficient burning of fuel thanoccurs in heaters with conventional hemispherical catalytic elements.Further, by maintaining a major portion of the combustion area in agenerally upright side wall wherein the shape of the side wall isstraight along the direction of flow of combustion air, most of thecombustion takes place at the side wall and may be radiated through aprotective canopy provided with large openings to heat persons gatheredaround the heater by radiation.

Having thus described in detail the preferred embodimerit of theinvention, persons skilled in the art will be able to modify certain ofthe structure which has been illustrated and to substitute equivalentelements for those which have been disclosed, while continuing topractice the principle of the invention; and it is, therefore, intendedthat all such modifications and substitutions be covered as they areembraced within the spirit and scope of the appended claims.

We claim:

1. ln a portable liquid fuel catalytic heater, the improvementcomprising: a catalytic element having an upright frusto-conical sidewall defining a vertical axis of symmetry and a top integral therewithfor partially defining said fuel vapor chamber, the outer surface ofsaid side wall being substantially straight along upright paths definingthe direction of combustion air flow and comprising between 50 andpercent of the total combustion surface of said catalytic element andlines on the outer surface of said side wall extending parallel to saidaxis defining an included angle with the vertical in the range between 0and 15, the combustion per unit area being appreciably greater on saidside wall than on said top; a protective canopy over said catalyticelement and spaced outwardly therefrom to provide a space for the flowof combustion air, said canopy defining a plurality of aperturesextending along substantially the entire height of and spaced about thecircumference of the side wall portion of said catalytic element, thetotal area of said apertures comprising at least 50 percent of the areaof said canopy adjacent said side wall element to facilitate lateralheating by radiation; and means including a wick for supplying liquidfuel to said chamber where said fuel is vaporized.

2. The heater ofclaim 1, wherein said included angle is approximately 3with the vertical 3. The heater of claim 1, wherein said apertures insaid canopy comprise a plurality of vertically elongated aperturesspaced about the periphery of said canopy and each extending from apoint above the sidewall portion of said catalytic element to a pointbelow said sidewall portion.

4. The system of claim 1, wherein the top of said catalytic element isslightly domed to facilitate lighting of said element in a wind, theheight of said side wall being at least four times greater than theheight of said domed top.

5. The heater of claim 1, wherein said catalytic element includesnon-combustible fibers molded to form a porous element impregnated atits surface with a catalyst.

6. The heater of claim 1 further comprising a wire mesh on the exteriorof said catalytic element for covering the same, said element being freeof any interior support to thereby reduce the mass thereof andfacilitate rapid starting.

1. In a portable liquid fuel catalytic heater, the improvementcomprising: a catalytic element having an upright frusto-conical sidewall defining a vertical axis of symmetry and a top integral therewithfor partially defining said fuel vapor chamber, the outer surface ofsaid side wall being substantially straight along upright paths definingthe direction of combustion air flow and comprising between 50 and 75percent of the total combustion surface of said catalytic element andlines on the outer surface of said side wall extending parallel to saidaxis defining an included angle with the vertical in the range between0.degree. and 15.degree., the combustion per unit area being appreciablygreater on said side wall than on said top; a protective canopy oversaid catalytic element and spaced outwardly therefrom to provide a spacefor the flow of combustion air, said canopy defining a plurality ofapertures extending along substantially the entire height of and spacedabout the circumference of the side wall portion of said catalyticelement, the total area of said apertures comprising at least 50 percentof the area of said canopy adjacent said side wall element to facilitatelateral heating by radiation; and means including a wick for supplyingliquid fuel to said chamber where said fuel is vaporized.
 2. The heaterof claim 1, wherein said included angle is approximately 3.degree. withthe vertical.
 3. The heater of claim 1, wherein said apertures in saidcanopy comprise a plurality of vertically elongated apertures spacedabout the periphery of said canopy and each extending from a point abovethe sidewall portion of said catalytic element to a point below saidsidewall portion.
 4. The system of claim 1, wherein the top of saidcatalytic element is slightly domed to facilitate lighting of saidelement in a wind, the height of said side wall being at least fourtimes greater than the height of said domed top.
 5. The heater of claim1, wherein said catalytic element includes non-combustible fibers moldedto form a porous element impregnated at its surface with a catalyst. 6.The heater of claim 1 further comprising a wire mesh on the exterior ofsaid catalytic element for covering the same, said element being free ofany interior support to thereby reduce the mass thereof and facilitaterapid starting.